Hygrostat



1959 B. GUSTAVSSON 2,887,544

' HYGROS'IAT Filed Feb. es, 1956 INVENY'OR BERTI L GUSTAVSSON UnitedStates Patent HYGROSTAT Bertil Gustavsson, Jonkoping, Sweden, assignorto A B Svenska Fliiktfabriken, Stockholm, Sweden Application February 6,1956, Serial No. 563,659

Claims priority, application Sweden February 9, 1955 4 Claims. (Cl.200--61.06)

The present invention relates to a novel and improved design of ahygrostat with two moisture responsive means consisting of bundles ofhair or the like and impulse means for an outer circuit actuated by saidresponsive means and enclosed in a casing, one of the said responsivemeans being at its one end connected with a support that may beadjustable and is attached to said casing, and the other responsivemeans being at its corresponding end, within said casing, connected withsaid impulse means, while outside the casing the responsive means areeach connected with one end of a lever resting on an edge at the end ofa bar journalled in said casing. According to the characteristics ofthis invention the bar supporting said lever can be axially displaced byturning a nut engaging the end of the standard being located within saidcasing, which end is provided with a threaded portion and that the nutis turned by means of a knob arranged outside the casing and providedwith a scale with graduation in degrees of relative humidity. Theinvention makes it possible that the operation range of the hygrostatcan easily be varied without any need of demounting the hygrostat orparts thereof. According to a preferred embodiment of the invention, thejournalled portion of the bar has, at each side of the wall of saidcasing, a noncircular, preferably rectangular cross-section, whichprovides the most simple manner of guiding the bar during its movements.

The invention will now be described more in detail with reference to theaccompanying drawing, which illustrates an exemplifying embodiment of ahygrostat according to the invention.

In the drawing, reference numeral 1 designates a casing enclosing animpulse means which in the shown embodiment is a so called micro-switch9. Numerals 3 and 4 designate two moisture responsive means consistingof hair bundles or some other hygroscopic material. The means 3 is atits one end connected with a support 3a that is resiliently attached tothe casing 1 via a spring 2. The corresponding end of the other moistureresponsive means, 4, is fastened to a support 4a connected over the rod8 with the impulse means 9. The opposite ends, 3b and 411, respectively,of the moisture responsive means are attached to the one end of a lever6 resting on an edge b at the top of a bar 5 the opposite end 5a ofwhich is journaled and guided in the casing 1. Numeral 7 designates aperforated protective envelope that could suitably be arranged round themoisture responsive means. The end 5a of the bar has a threaded portion11 engaging a nut 12. The nut is secured to and can be rotated by meansof a knob 13 having a scale of degrees 14. Upon rotation of the nut 12the bar 5 is moved axially against the action of spring whereby thedesired operation range of the hygrostat can be adjusted. Theconstruction of the impulse means can be varied within the scope of theinvention.

What I claim is:

1. In a hygrostat adapted to control the relative humidity of a gaseousmedium flowing in a duct, comprising a casing mounted outside of saidduct, an elongated bar threaded at one end within said casing andslidably mounted for longitudinal movement through one end wall of saidcasing and projecting therebeyond into said duct; an equalizing leverpivotally supported on the projecting end of said bar as a fulcrum; twosets of humidity responsive means, each set being connected at one endto said lever, extending within said duct substantially parallel to saidbar, and terminating at the other end in a member extending through saidone end wall into said casing; an adjustable support in said casing forone of said members; switch means supporting the other of said membersand operated by said member in response to changes in relative humidityof the gaseous medium in said duct; an auxiliary circuit connected tosaid switch means to control the relative humidity of said medium; andmeans to longitudinally displace said elongated bar comprising a rotaryelement journalled for rotation in the opposite end wall of said casinghaving a nut engaged with the threaded portion of said bar in saidcasing, and an actuating knob on said rotary element outside of saidcasing, said knob having a scale graduated in degrees of relativehumidity.

2. A hygrostat according to claim 1 wherein said elongated bar has anon-circular cross-section in the portion which projects through saidone end wall of the casing, and wherein further said end wall is formedwith a corresponding non-circular aperture to slidably support said baragainst rotation.

3. A hygrostat according to claim 2 wherein said noncircularcross-section is rectangular.

4. In a hygrostat adapted to control the relative humidity of a gaseousmedium flowing in a duct, comprising a casing mounted outside of saidduct, means in one end wall of said casing defining a rectangularaperture, an elongated bar threaded at one end within said casing,having a central portion of rectangular cross section slidably mountedfor longitudinal movement through said aperture in the one end wall ofsaid casing, and projecting therebeyond into said duct; a springsurrounding said bar within said casing and seated at one end againstsaid one end wall and at the other end on said bar to bias said barlongitudinally toward the opposite end wall of the casing; an equalizinglever pivotally supported on the projecting end of said bar as afulcrum; two sets of humidity-responsive means, each set being connectedat one end to said lever, extending within said duct substantiallyparallel to said bar, and terminating at the other end in a memberextending through said one end wall into said casing; an adjustablesupport in said casing for one of said members; switch means supportingthe other of said members and operated by said member in response tochanges in relatively humidity of the gaseous medium in said duct; anauxiliary circuit connected to said switch means to control the relativehumidity of said medium; and means to longitudinally position saidelongated bar against the bias of said spring comprising a rotaryelement journalled for rotation in said opposite end wall of said casingand having a nut engaged with the threaded portion of said bar in saidcasing, and an actuating knob on said rotary element outside of saidcasing, said knob having a scale graduated in degrees of relativehumidity.

References Cited in the file of this patent UNITED STATES PATENTS1,962,098 Zellhoefer June 5, 1934 1,998,340 Streb et al. Apr. 16, 19352,041,658 Hodge May 19, 1936 2,191,630 Shutts Feb. 27, 1940 2,503,273Johnson Apr. 11, 1950 2,780,687 Keenan Feb. 5, 1957 FOREIGN PATENTS112,184 Sweden Oct. 24, 1944 444,831 Great Britain Nov. 18, 1935

